Developments of alternative energy resources (e.g., solar energy, biofuel, hydropower, wind power etc.) have been encouraged for years to cope with arising energy problems related to vastly consumptions of fossil fuels. Among many possible resources, plant biomass is of particular interest as it is renewable. Plant mass contains a high amount of cellulose, a starting material for making biofuel. To convert cellulose to biofuel, it is first degraded to fermentable sugars, such as cellobiose and glucose, by the cellulolytic system of microorganisms. This system includes three major types of hydrolases, i.e., endoglucanases (EC 3.2.1.4), exoglucanases (EC 3.2.1.91), and β-glucosidases (EC 3.2.1.21). Although many glucosidases have been isolated from various microorganisms, their efficiencies are not satisfactory. Thus, there is a need for a high efficient glucosidase.